The invention relates to a method for the operation of an exhaust gas aftertreatment system for an internal combustion engine, in particular for a diesel engine, a device for performing the method, and to a vehicle, in particular a commercial vehicle, for performing the method and/or having the device.
The provision of a particle filter in an exhaust tract of an internal combustion engine which serves to filter out from the exhaust gas and to store particles, in particular carbon particles, contained in the exhaust gas from the internal combustion engine, is known. The regeneration of such a particle filter can be accomplished, for example, through combustion of the particles stored in the particle filter. For this combustion, high temperatures (approximately 600° C.) are necessary, which cannot routinely be attained in conventional operation of the internal combustion engine, in particular of a diesel engine. In order to be able nevertheless to burn the particles accumulated in the particle filter, measures are usually taken to briefly increase the temperature of the particle filter. Such measures may include an increase in the quantity of fuel injected, for example, or heating of the particle filter by a heating device or the backflow of exhaust gas. Another known way of regenerating a particle filter is the continuous regeneration trap (CRT). In this regeneration of the particle filter an oxidation catalytic converter, which serves to convert the nitrogen monoxide contained in the exhaust gas from the diesel engine into nitrogen dioxide, is usually arranged in the exhaust tract upstream of the particle filter, viewed in the direction of flow of the exhaust gas. Even at low exhaust gas temperatures (approximately 250° C.), the nitrogen dioxide formed reacts with the carbon particles stored in the particle filter, thereby regenerating the particle filter. This usually ensues according to the following equation for the reaction:2NO2+C→2NO+CO2 
In addition to the CRT, it is also known to provide an SCR-active catalytic material, which reduces the nitrogen oxides contained in the exhaust gas from the internal combustion engine using ammonia as reducing agent. The ammonia is usually introduced into the exhaust tract upstream of the particle filter, viewed in the direction of flow of the exhaust gas, in the form of an aqueous urea solution (“AdBlue”). The reduction of the nitrogen oxides usually ensues according to the following equations for the reaction:4NH3+4NO+O2→4N2+6H2O2NH3+NO+NO2→2N2+3H2O4NH3+3NO2→3.5N2+6H2O
As is apparent from the stated equations for the reaction, in a particle filter which is to be continuously regenerated, i.e., using a CRT, and which also comprises a SCR catalytic material, a situation arises in which there is competition vis-a-vis the nitrogen dioxide contained in the exhaust gas. In order to counteract such a competitive situation, DE 10 2014 001 880 A1 discloses the arrangement of a further SCR catalytic converter downstream of the particle filter, viewed in the direction of flow of the exhaust gas, and the similar introduction of an aqueous urea solution into the exhaust tract between the particle filter and the further SCR catalytic converter, viewed in the direction of flow of the exhaust gas. This allows the quantity of aqueous urea solution introduced into the exhaust tract upstream of the particle filter to be reduced in such a way as to ensure the continuous regeneration of the particle filter. The desired reduction of the nitrogen oxides contained in the exhaust gas is ensured by the aqueous urea solution introduced into the exhaust tract downstream of the particle filter and upstream of the further SCR catalytic converter.